1. Field of the Invention
The present invention relates to a piston type compressor with a suction reed valve stopper, adapted for use in a unit for air-conditioning a vehicle passenger compartment, and more particularly, to a piston type compressor with a suction reed valve stopper which stops the movement of the suction reed valve during each suction stroke of the pistons while acquiring an adequate amount of opening for refrigerant suction and suppressing noisy vibration of the suction reed valves.
2. Description of the Related Art
Many piston type compressors, such as a swash plate type compressor and a wobble plate type compressor are known. For example, U.S. Pat. Nos. 4,403,921 to Kato et al discloses a swash plate type compressor with a double-acting reciprocatory pistons and a suction reed valve mechanism; and 4,428,718 to Skinner discloses a wobble plate type compressor with compressing pistons and suction reed valves formed integrally with a suction valve disk. For example, the known swash plate type compressor of U.S. Pat. No. 4,403,921 includes a cylinder block having therein a plurality of cylinder bores serving as compression chambers for permitting pistons to be reciprocated therein to compress a refrigerant gas. The ends of the cylinder block are closed by front and rear housings, via valve plates, respectively, so that suction and discharge chambers are formed in each of the front and rear housings. The suction chambers are fluidly communicated with the compression chambers through suction ports formed in the valve plates and suction reed valves arranged on an inner side of respective valve plates, and the discharge chambers are fluidly communicated with the compression chambers through discharge ports formed in the same valve plates and discharge valves arranged on an outer side of respective valve plates. The valve plates are also formed with inlet ports for permitting a refrigerant gas returning from the outer air-conditioning circuit to flow into the suction chambers, and outlet ports for permitting a compressed refrigerant gas to flow from the discharge chambers into the air-conditioning circuit. The suction reed valves which are formed integrally with a suction valve disk made of resilient metallic material, such as a stainless steel plate, have a thickness of between 0.2 and 0.4 mm and are formed to be resiliently movable between a closed position in which they are in contact with the valve plates for closing the suction ports and an opening position in which the suction reed valves are apart from the valve plates for opening the suction ports. When the suction reed valves are moved to the opening position, the end of each suction reed valve abuts against a stop formed as a recessed seat in the axial end face of the cylinder block. That is, the amount of movement of the suction reed valves is determined by the depth of the recessed seat from the axial end face of the cylinder block. The conventional depth of the recessed seat acting as the stop is set at approximately 1.4 mm, and the seating surface of the recessed seat is formed as a plane surface in parallel with the valve plates. However, it was found that the conventional construction of the suction reed valve stop formed as the recessed seat brings about such a problem wherein during each process of the movement of the suction reed valves from the closing position in contact with the valve plates to the opening position abutting against the bottom of the recessed seats, the suction reed valves are subjected to a self-excited vibration caused by the flow of a refrigerant sucked into the compression chambers due to the suction stroke of the pistons. The vibration causes sound or noise to be generated at the evaporator of the air-conditioning circuit. Particularly, when the compressor is in an operating condition such that the amount of circulating flow of refrigerant in the air-conditioning circuit is small, i.e., either during idle operation of the compressor or during operation at a low rotational speed, the end of each suction reed valve is not sufficiently moved to the opening position in which it is stably seated on and stopped by the bottom of the recessed seat, and accordingly, the suction reed valve is subjected to irregular vibration under the influence of a change in the flow of refrigerant gas sucked into the compression chamber. As a result, the vibration of the suction reed valves causes a sound or clatter.
On the other hand, if the depth of each recessed seat is reduced, for example, to less than 1 mm, the above-mentioned vibration might be suppressed. But, since the amount of movement of the suction reed valves from the closed position to the opening position must be decreased, a sufficient refrigerant cannot be then introduced into the compression chambers during the suction stroke of the pistons, and accordingly, the refrigerant gas in the compression chambers is subjected to an excess compression, and the temperature of the discharged refrigerant unfavorably rises.